Helically corrugated waveguide transition section



June 8, 1965 H. MARTIN ETAL 3,188,586

HELICALLY CORRUGATED WAVEGUIDE TRANSITION SECTION Filed May 14, 1963 FIQZ I NVENTORS. #smur MART/IV qua/rm Mal/mus ATTORNEY United States Patent 3,188,586 HELICALLY CORRUGATED WAVEGUIDE TRANSITIGN SECTION Helrnut Martin, Hannover, and Gunter Mohring, Langenhagen, Hanuover, Germany, assignors to Hackethal- Drahtund Kabel-Werke Aktiengesellschaft Filed May 14, 1963, Ser. No. 280,315 7 Claims. (Cl. 333-95) This invention relates to corrugated waveguides, and more particularly concerns the junction portions thereof.

It is known that in the transmission of electro-magnetic waves through waveguides from one section thereof to another can be seriously efiected if a cross-sectional or dimensional change takes place, thus giving rise to a discontinuity therein. These difliculties are primarliy due to changes in the reflection characteristics at the transition point and special adjustments must be made to avoid this condition.

On the one hand, the input and output connections of amplifiers, transmitters and receivers usually have a rectangular cross section; on the other hand, waveguides of similar cross section are expensive to produce in long lengths and are also diflicult to handle. Therefore, waveguides are more commonly of a circular or elliptical crosssection. It follows that under the circumstances, junctions must be used to couple the circular or elliptical waveguides of substantial length with the rectangular section inputs or outputs.

The use of corrugated tubes as waveguides for electromagnetic waves is favored because of the absence of crosssectional distortion at bend portions thereof. Also, corrugated tubes are more readily bent than smooth wall tubes. Despite such advantages, corrugated waveguides present discontinuity problems at their juncture points and conventional approaches do not overcome such problems.

Accordingly, an object of this invention is to provide an improved junction structure for corrugated waveguides whereby to couple the same in an improved manner to wave guides of differing section or dimensions.

Briefly, the invention contemplates a Waveguide junction which is applicable to corrugated types of waveguides wherein the junction comprises a corrugated section at one end thereof and a smooth walled, non-corrugated section at the other end thereof; the corrugations of the corrugated section extending to the joinder of the corrugated and non-corrugated sections. In the corrugated section of such junction, the depth of the corrugations decrease in a progressive manner along the axial extent of the junction to the joinder portion of the corrugated and non-corrugated sections.

Other objects of this invention will in part be obvious and in part hereinafter pointed out.

In the drawing, FIG. 1 is a side elevational view of a waveguide junction embodying the invention, with parts in section; and

FIG. 2 is a side elevational view similar to that of FIG. 1, showing an alternative embodiment of the invention.

Referring to FIG. 1, 1t) designates a waveguide junc tion of generally tubular form, comprising a corrugated section 12 having helical corrugations extending from end 14 to a point 16 from which extends a smooth walled, non-corrugated section 18. The junction end 14 is generally integrally connected to a corrugated wave guiide, not shown, which has corrugations of uniform depth along the axial extent thereof, the depth of such corrugations being substantially equal to the depth of the corrugations 19 immediately adjacent junction end 14.

As indicated in FIG. 1, the successive corrugations along the axial extent of junction progressively decrease in depth and such depth is substantially zero at point 16. The waveguide junction 20, shown in .FIG. 2 is similar to junction 10 except that the decrease in the depth of the corrugations in section 12' occurs in a stepwise manner in increments of axial length, as indicated at 21, 22, 23 and 24.

Within each axial increment, the depth of corrugation is substantially uniform. However, the corrugation depth in one increment is less than the depth of corrugation in the preceding increment. Thus, the corrugations in increment 22 have a depth less than that of increment 21; etc. Beyond point 16, the waveguide junction 20 has a smooth, uncorrugated wall 18, as previously described.

The axial distance over which the corrugation depth diminishes depends upon the frequency bandwidth or operating wavelength. If the corrugation depth decrease is continuous as shown in FIG. 1, it amounts to 2L (operating wave lengths) extending from end 14 to point 16. With the step-by-step pattern of corrugation depth decrease, as shown in FIG. 2, optimum results are attained when each of the increments 21-24 has an axial extent of L/ 4 (operating wavelengths). It is understood that that the junction may have more than four increments, but each increment has an axial extent of L/4 (operating wave lengths).

Thus, there is provided waveguide junctions 10, 20 which include at one end smooth, non-corrugated wall portions of circular or elliptical cross-section which may be connected by a conventional coupling to a wave guide or waveguide portion of a device which is of a rectangular or quadratic cross-section.

The waveguide junctions described above can be manufactured by' conventional procedures, wherein the change of corrugation depth is achieved by stepwise or continuous adjustment of the corrugating tool operating on the smooth walled tubing which is converted into corrugated form. The junctions may be secured to coupling means or waveguides proper by welding, flanging or other joinder procedures known in the art.

It is understood that all matter herein disclosed is to be deemed illustrative and not by way of limitation except as set forth in the appended claims.

What is claimed is:

1. A waveguide junction for the transmission of electromagnetic waves therethrough comprising a tubular member having a transversely corrugated section and a smooth walled section extending from one end of said corrugated section, the depth of the corrugations of said corrugated section progressively decreasing as said corrugations approach the juncture of said corrugated and smooth walled sections, said corrugated section including the corrugations of progressively decreasing depth having an axial extent of at least two operating Wave lengths to its juncture with the smooth walled section. a

2. A Waveguide junction as in claim 1 wherein the progressive decrease in depth of the corrugations is continuous.

3. A Waveguide junction as in claim 1 wherein the progressive decrease in depth of the corrugations is stepwise.

4. A waveguide junction as in claim 3 wherein the stepwise decrease in corrugation depth occurs in successive axial increments, each increment having an axial extent of one quarter of an operating Wavelength.

5. A waveguide junction as in claim 1 wherein said corrugated section comprises helically extending corruga- Patented June 8,1965

member of arcuate cross section, said member comprising first and second axial sections in end abutting relation, the first tubular section being transversely corrugated and having an axial extent of at least two operating wave lengths, the second tubular section having a smooth, uncorrugated wall, the corrugations in said first tubular section being of progressively decreasing depth from the outer end thereof to the juncture of said tubular sections, the corrugation depth at the juncture of said tubular sections being zero.

References Cited by the Examiner UNITED STATES PATENTS Holmes 153-72 Picece et al 15371 Duenas et a1 1S3-71 McCormick 138-122 Humphrey 15371 10 HERMAN KARL SAALBACH, Primary Examiner. 

1. A WAVEGUIDE JUNCTION FOR THE TRANSMISSION OF ELECTROMAGNETIC WAVES THERETHROUGH COMPRISING A TUBULAR MEMBER HAVING A TRANSVERSELY CORRUGATED SECTION AND A SMOOTH WALLED SECTION EXTENDING FROM ONE END OF SAID CORRUGATED SECTION, THE DEPTH OF THE CORRUGATIONS OF SAID CORRUGATED SECTION PROGRESSIVELY DECREASING AS SAID CORRUGATED APPROACH THE JUNCTION OF SAID CORRUGATED AND SMOOTH WALLED SECTIONS, SAID CORRUGATED SECTION INCLUDING THE CORRUGATIONS OF PROGRESSIVELY DECREASING DEPTH HAVING AN AXIAL EXTENT OF AT LEAST TWO OPERATIVE WAVE LENGTHS TO ITS JUNCTURE WITH THE SMOOTH WALLED SECTION. 